The present invention relates generally to cardiovascular catheters and also to circulatory support systems. More particularly, it relates to a system and method for performing catheter based medical procedures, such as balloon angioplasty, stent placement, atherectomy, valvuloplasty and other therapeutic procedures, with protective circulatory support in order to minimize the risk to the patient from such procedures. The system and methods of the present invention serve to expand the patient population treatable by catheter based procedures to include patients who might otherwise require open chest surgery with cardiopulmonary bypass and also to high risk patients who might not be acceptable candidates for these surgical alternatives.
Many catheter based diagnostic and therapeutic procedures have been developed in the areas of interventional cardiology, interventional radiology, interventional neuroradiology and electrophysiology. Examples of such procedures include balloon angioplasty, stent placement, atherectomy and valvuloplasty. These and many other catheter based diagnostic and therapeutic procedures can benefit from the system and methods of the present invention, particularly in high risk patients.
Balloon angioplasty is a procedure in which a small, cylindrical balloon is mounted on an elongated catheter which is inserted into a stenosis or a narrowing in a blood vessel and inflated to dilate the stenosis and improve blood flow. Balloon angioplasty can be applied to coronary arteries, carotid arteries and peripheral arteries, as well as other body passages. Patents which describe apparatus and methods for performing balloon angioplasty include U.S. Pat. Nos. 4,195,637; 4,323,071; 4,545,390; 4,545,390; 4,538,622; 5,055,024; 4,490,421; 4,616,653; 5,133,364; 5,060,660; 5,031,636; 4,922,923; 4,917,103; 4,875,489; 4,827,941; 4,762,129; 4,988,356; 4;748;982; 5,040,548 and 5,061,2,73. The specifications of these patents and all other patents and patent applications mentioned herein are hereby incorporated by reference in their entirety.
Valvuloplasty is a closely related procedure in which a somewhat larger balloon or balloons are inserted into a stenosis in a heart valve and inflated to open the stenosis and improve blood flow through the valve. Valvuloplasty can be applied to the aortic valve, mitral valve, tricuspid valve or pulmonic valve. Patents which describe apparatus and methods for performing valvuloplasty include U.S. Pat. Nos. 4,787,388; 4,796,629; 4,909,252; 5,295,958.
Atherectomy is an alternative procedure to balloon angioplasty in which, rather than simply dilating the stenosis, some or all of the stenotic material is removed to debulk the stenosis and improve blood flow. Atherectomy includes both rotational atherectomy in which stenotic material is removed symmetrically about the catheter and directional atherectomy in which stenotic material is selectively removed from certain parts of the blood vessel. Patents which describe apparatus and methods for performing atherectomy include. U.S. Pat. Nos. 4,323,071; 5,071,425; 4,781,186; RE 33,569; 4,290,427; 4,315,511; 4,574,781; 4,621,636; 4,890,611; 5,368,603; 3,730,183; 5,071,424; 5,156,610; 5,282,484; 5,211,651; 5,267,955; 5,195,956; 5,178,625; 4,589,412; 4,854,325; 4,883,460; 4,273,128.
Stent placement, is a procedure often very closely associated with balloon angioplasty and also sometimes with atherectomy. Vascular stents, also known as endovascular prostheses, are small, generally cylindrical, metallic or polymeric scaffolds that are implanted within the lumen of a blood vessel to maintain patency of the lumen. Elective stent placement may be done as an adjunct to balloon angioplasty or atherectomy or emergency stent placement may be done in the case of a failed angoplas or atherectoiny. Stents can be applied to coronary arteries, carotid arteries and peripheral arteries, as well as other body passages. Stent grafts or covered stents resemble standard vascular stents with the addition of a prosthetic vascular wall over the metallic or polymeric scaffold of the stent. Patents which describe apparatus and methods for performing stent placement include. U.S. Pat. Nos. 5,041,126; 4,856516; 5,037,392; 5,683,452; 5,578,072; 5,571,171; 5,522,880; 5,360,443; 5,102,417; 4,776,337; 4,739,762; 4,733,665; 55674,278; 5,782,855; 5,780,807; 5,766,710; 5,766,239; 5,766,238; 5,759,192; 5,738,674; 5,735,893; 5,733,330; 5,728,158; 5,725,572; 5,725,549; 5,707,385; 5,700,286; 5,681,346; 5,649,977; 5,649,952; 5,637,113; 5,632,840; 5,629,077; 5,618,299; 5,607,444; 5,605,696; 5,603,721; 5,593,434; 5,591,197; 5,569,295; 5,556,413; 5,546,646; 5;514,154; 5,507,768; 5,498,240; 5,476,505; 5,458,615; 5,458,605; 5,456,667; 5,443,500; 5,443,458; 5,441,515; 5,437,083; 5,423,885; 5,421,955; 5,415,637; 5,409,495; 5,391,172; 5,360,401; 5,344,426; 5,242,399; 5,158,548.
Electrophysiology diagnostic studies and therapeutic ablation procedures are used for diagnosis and treatment of various cardiac arrhythmias. Patents that describe apparatus and methods for performing electrophysiology procedures include U.S. Pat. Nos. 4,699,147; 5,327,889; 4,960,134; 5,140,987; 4,522,212; 4,660,571; 4,664,120; 5,125,896; 5,104,393.
Other catheter based procedures will also benefit from the system and methods of the present invention, particularly in high risk patients. For example: transmyocardial revascularization, U.S. Pat. Nos. 4,658,817; 5,125,924; 5,125,926, patent ductus arteriosus closure, septal defect repair, U.S. Pat. Nos. 3,874,388; 4,874,089, intravascular ultrasonic imaging, U.S. Pat. Nos. 5,000,185; 4,794,931; 5,029,588; 4,024,234; 4,917,097; 5,167,233; 5,368,037; 5,190,046; WO 94/16625, laser angioplasty or ablation, U.S. Pat. Nos. 5,354,294; 5,366,456; 5,163,935; 4,740,047; 5,242,438; 5,147,353; 5,242,437; 5,188,634; 5,026,366; 4,788,975.
The system and methods of the present invention find particular use in performing catheter based medical procedures, such as balloon angioplasty, stent placement, atherectomy, valvuloplasty and other therapeutic procedures, on high risk patients. High risk patients in this context include extremely young or extremely elderly patients and patients whose cardiopulmonary functions are severely compromised.
In addition to the above examples, patients with severe cardiovascular disease or other complicating factors, such as patients requiring balloon angioplasty, stent placement or atherectomy in highly critical portions of the vasculature will particularly benefit from these procedures. Examples of highly critical portions of the vasculature may include: lesions in the ostia of the coronary arteries, the left main coronary artery, diseased saphenous vein grafts and totally occluded coronary arteries or the carotid arteries.
Because of the risks to the patient, the aforementioned catheter procedures are usually performed while a surgical backup team stands by on call with a surgical suite reserved for emergency surgery in the event that the procedure fails or if dangerous complications arise. This gives rise to two specific problems, surgical backup may not always be logistically possible and surgical backup is costly. One example of where surgical backup is not logistically possible, is when the catheter procedure is being performed in an emergency situation.
Surgical backup is also a significant economic burden for the patient, the hospital and the entire medical system. The timing for emergency surgery is very critical, although the surgical backup team only needs to be relied upon in a very small percentage of cases, it is necessary to have the surgical team and the operating room ready immediately. In particular, where a failed procedure results in severe complications, such as cardiac arrest, myocardial infarction or cerebral ischemia or embolization, there is only a narrow window of response time available to perform emergency surgery in order to save the patient.
Therefore, because of the conflicting pressures of economics and of patient safety, it would be extremely desirable to reduce the reliance on surgical backup for high risk catheter based procedures. The present invention is intended to provide a margin of protection that mitigates the risk to the patient and extends the acceptable time window for response when emergencies or complications arise.
Various strategies have been proposed to mitigate the danger to patients during high risk catheter procedures. These proposed strategies have include perfusion balloon catheters, intra-aortic balloon pumps, percutaneous or femoral-femoral cardiopulmonary bypass, retrograde coronary perfusion, and single-balloon intra-aortic occlusion catheters for cardioplegic arrest. None of these approaches provide all of the benefits of the present invention.
Perfusion balloon catheters, U.S. Pat. Nos. 5,573,508; 5,573,509; 5,344,402, are angioplasty catheters which have been adapted to provide blood flow downstream of the dilatation balloon to prevent ischemia of the myocardium during prolonged inflation of the balloon. This approach protects only the myocardium at risk of infarction downstream from the dilatation site. It does not provide global circulatory protection or selective cerebral protection in the event of low cardiac output or cardiac arrest. It also does not provide for elective cardiac arrest or a transition to cardiopulmonary bypass in the event that surgical intervention becomes necessary. Perfuision balloon catheters can be used in conjunction with the system and methods of the present invention.
Intra-aortic balloon pumps (IAPB) are balloon catheters that provide counterpulsation to reduce the cardiac pumping load and to augment coronary artery circulation. An IAPB only assists the beating heart in providing circulation and therefore would not provide global circulatory protection or selective cerebral protection in the event of cardiac arrest. An IAPB also does not provide for elective cardiac arrest or a transition to full cardiopulmonary bypass in the event that surgical intervention becomes necessary.
Percutaneous or femoral-femoral cardiopulmonary bypass, U.S. Pat. Nos. 3,513,845; 4,540,399; 5,0119469 is an approach to cardiopulmonary bypass (CPB) which uses peripherally inserted arterial and venous cannulas to avoid the necessity of a median sternotomy. This circulatory support method has been suggested for use in high risk angioplasty cases. However, this method affords no provision for safe, elective (e.g. cardioplegic) cardiac arrest, nor does it provide for prioritized cerebral protection.
Retrograde coronary perfusion or coronary retroperfusion (e.g. U.S. Pat. Nos. 5,451,207; 5,451,207; 5,655,548; 5,597,377; 5,533,957; 5,423,745; 5,401,244; 5,395,331; 5,324,260; 5,290,231; 5,059,167; 5,033,998; 5,024,668; 5,011,468; 4,934,996; 4,927,412; 4,917,667; 4,865,581; 4,850,969; 4,648,384; 4,459,977; 4,290,428) has been suggested for the treatment of myocardial ischemia, for myocardial protection during high risk catheter procedures and for administering cardioplegic arrest. For example, U.S. Pat. No. 5,451,207 describes the use of retrograde coronary perfusion for myocardial protection during a coronary atherectomy procedure. Retrograde coronary perfusion, however, requires additional cannulation in order to make the transition to cardiopulmonary bypass and it does not provide prioritized cerebral protection.
Single-balloon intra-aortic occlusion catheters, e.g. WO 96/30072, have been suggested for myocardial protection and for emergency or elective cardioplegic arrest during high risk catheter procedures. Single-balloon intra-aortic occlusion catheters of this type do not provide prioritized cerebral protection. U.S. Pat. No. 5,695,457 describes a system of coronary isolation catheters as a substitute for the single-balloon intra-aortic occlusion catheter for cardioplegia delivery and for use in high risk angiopiasty and other catheter procedures. This system also does not provide prioritized cerebral protection.
Another related technology involves cardiopulmonary support by selective aortic perfusion. U.S. Pat. Nos. 5,308,320, 5,383,854, 5,820,593 and 5,906,588 by Peter Safar, S. William Stezoski, and Miroslav Klain describe catheters that segment the aorta to perform differential perfusion. Other U.S. patent applications which address the concept of selective aortic perfusion include commonly owned, copending patent applications 08/909,293, filed Aug. 11, 1997; and 09/152,589 filed Aug. 11, 1998 to Safar et al.
Furthermore, U.S. Pat. Nos. 5,738,649, 5,827,237, 5,833,671; and commonly owned, copending patent applications 09/060,412, filed Apr. 14, 1998 by John A. Macoviak; and 08/665,635, filed Jun. 17, 1996; by John A. Macoviak and Michael Ross; and 60/067,945, filed Dec. 8, 1997, by Bresnahan et al. and 60/084,835, filed Apr. 25, 1997 by Macoviak et al. describe circulatory support systems and methods of use for isolated segmental perfusion. Perfusion shunt devices and deflectors for perfusing an isolated organ system while the beating heart supplies the remainder of the circulatory system are described in commonly owned, copending patent application 09/212,580, filed Dec. 14, 1998 and 60/116,836, filed Oct. 1, 1998 by Macoviak et al. In addition, commonly owned, copending patent application 09/306,555, filed May 6, 1999 by Macoviak et al. describes a circulatory support system and method of use for isolated segmental perfuision. These patent applications and all other patents referred to herein are hereby incorporated by reference in their entirety. Selective perfusion can be used to prioritize the flow of oxygenated blood or other protective fluids to the various organ systems, with different temperatures or compositions, for achieving optimal preservation of all organ systems within the body.
In keeping with the foregoing discussion, the present invention provides a system and methods for performing catheter based procedures on high risk patients that mitigate the risk to the patient and extend the acceptable time window for response when emergencies or complications arise. The system is useful in a number of operating modes, including: stopped heart catheter procedures, concurrent surgical interventions, sequential surgical interventions, catheter based interventions and as a safety backup or bail out system in beating heart catheter procedures. The system provides cardiopulmonary support for the patient""s circulatory system and prioritized protection for the patient""s cerebral and coronary circulation. The system, when used according to the methods of the present invention, allows a patient to be placed in varying degrees of suspended animation during the catheter procedure. Furthermore, when emergencies or complications arise, implementation of these procedures are intended to protect the patient""s critical organ systems and to extend the safe period of time to initiate a surgical intervention.
The system combines a therapeutic or diagnostic catheter subsystem, which may take one of many known forms, with a selective aortic perfusion and cardiopulmonary bypass subsystem. The therapeutic or diagnostic catheter subsystem may take the form of an angioplasty subsystem, typically an angioplasty balloon catheter, a guiding catheter and a guidewire; a stent delivery subsystem, typically a stent delivery catheter, a stent, a guiding catheter and a guidewire; an atherectomy subsystem, typically an atherectomy catheter, a guiding catheter and a guidewire; a valvuloplasty subsystem, typically a valvuloplasty balloon catheter and a guidewire; or other known diagnostic or therapeutic catheter systems. The selective aortic perfusion and cardiopulmonary bypass subsystem generally includes catheters and/or cannulas for draining blood from the patient""s venous or arterial system, a perfusion pump, a blood oxygenator, at least one blood heatexchanger and catheters and/or cannulas for perfusing oxygenated blood into the patient""s arterial system. The arterial perfusion catheters and/or cannulas are especially configured to perform aortic segmentation and selective perfusion of the patient""s circulatory system.
In order to accomplish aortic segmentation, the arterial perfusion catheters and/or cannulas are constructed with at least a first external flow control member and a second external flow control member. Additional external flow control members may be included if further segmentation of the circulatory system is desired. The external flow control members may take the form of inflatable occlusion balloons and/or selectively deployable external catheter flow control valves. The external flow control members may be mounted on a single elongated catheter or cannula shaft or they may be mounted on separate catheter or cannula shafts for independent placement and deployment.
When the arterial perfusion catheters and/or cannulas are deployed, the first external flow control member is positioned in the patient""s ascending aorta between the coronary arteries and the brachiocephalic artery, and the second external flow control member is positioned in the patient""s descending aorta downstream of the aortic arch. The external flow control members are used to control or to occlude fluid flow through the lumenof the aorta so that the aorta is divided into an ascending aorta or coronary artery segment, an aortic arch or cerebral blood flow segment and a descending aorta or corporeal blood flow segment. Each of these segments is perfusable separately or in combination. This may be accomplished by perfusion lumens within the same catheter or cannula shaft as the external flow control members are mounted on and/or through separate perfusion cannulas that are inserted into each segment. Each of the segments may be perfused with oxygenated blood and/or other fluids having a composition and/or temperature chosen for optimal preservation of the organ systems fed by the blood vessels branching from the segments.
In one particular embodiment of the system, the first and second external flow control members are mounted off the upstream and downstream ends of a perfusion shunt lumen, which allows blood flow from the heart to flow past the aortic arch without entering the arch vessels. An arch perfusion lumen allows selective perfusion of the arch vessels.
In some embodiments of the system, one or more of the components of the therapeutic catheter subsystem may be integrated with the components of the selective aortic perfusion and cardiopulmonary bypass subsystem to create a dual purpose device. For example, an angioplasty or atherectomy guiding catheter may be combined with two external flow control members to create a combined guiding catheter and aortic segmentation catheter.
When the system is used for performing stopped heart catheter procedures on a patient, cardiopulmonary bypass is established and the heart is stopped by elective cardiac arrest, for example by cardioplegic or hypothermic arrest. While the heart is stopped, each segment of the circulatory system is perfused with an, appropriate fluid to optimize preservation of the organs within each segment. The catheters of the therapeutic catheter subsystem are introduced either coaxially or in parallel with the aortic perfusion catheters or cannulas and the catheter procedure is performed while the heart is stopped. After the catheter procedure is complete, the heart is restarted and the patient is weaned off of bypass. Performing the catheter procedure while the heart is stopped significantly mitigates the risk to the patient from the catheter procedure or its possible complications.
When the system is used as a safety backup or bail out system while performing beating heart catheter procedures, the patient is cannulated and partial cardiopulmonary bypass may be initiated for circulatory support, but full cardiopulmonary bypass is not initiated. The catheters of the therapeutic catheter subsystem are introduced either coaxially or in parallel with the aortic perfusion catheters or cannulas and the catheter procedure is performed in the normal manner while the heart is still beating. If the catheter procedure is successful and there are no complications, the patient is extubated at the end of the procedure and sent to the recovery room. However, if emergencies or complications arise during the catheter procedure, full cardiopulmonary bypass can be established immediately by simply stepping up the flow rate of the perfusion pump. In addition, selective aortic perfusion can be performed by deploying the external flow control members enabling the segmentation of the aorta whereby each segment can be perfused with a separate protective fluid. Through this method, the patient can be placed in varying degrees of suspended animation protecting the affected organ systems until an emergency surgical intervention can be performed. The different degrees of suspended animation include: partial bypass for circulatory support, full cardiopulmonary bypass and elective cardiac arrest, neuroplegic arrest, with or without elective cardiac arrest, and complete hypothermic circulatory arrest. The patient can be kept in the selected degree of suspended animation while the surgical team is assembled and while the operating room is being prepared or while the patient is being transferred to another facility with the necessary surgical resources.
The system may also be used for performing catheter procedures on a patient in conjunction with elective surgical interventions. For example angioplasty, stenting or atherectomy can be performed in conjunction with coronary artery bypass or cardiac valve replacement surgery. The catheter procedures may be performed concurrently with the surgical interventions while the heart is stopped or they can be performed sequentially before or after the surgical interventions while the heart is stoppe,d or while it is beating. If the catheter procedure is performed while the heart is beating, the selective aortic perfusion and cardiopulmonary bypass subsystem will be used as a safety backup system during the catheter procedure, as described above.